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Intent to Receive Influenza A (H1N1) 2009 Monovalent and Seasonal Influenza Vaccines --- Two Counties, North Carolina, August 2009

On September 15, 2009, the Food and Drug Administration approved the manufacture of four influenza A (H1N1) 2009 monovalent vaccines.* Before release of the first batches of the vaccine on September 30,intent to receive the vaccine was estimated at 50% among selected U.S. adult populations (1,2) and as high as 70% for children (2). However, studies in previous years of seasonal influenza vaccination in children, who might require 2 doses based on age and prior vaccination status, have indicated poor compliance with recommendations (3). To measure intent to receive H1N1 and seasonal influenza vaccines among children and adults, during August 28--29, 2009, the North Carolina Center for Public Health Preparedness, with state and local public health officials, conducted a community assessment in two counties. This report summarizes the results of that assessment, which determined that 64% of adults reported intent to receive H1N1 vaccine. In addition, 65% of parents reported intent to have all their children (aged 6 months to <18 years) vaccinated with H1N1 vaccine, and 51% said they would have all their children vaccinated with both H1N1 and seasonal influenza vaccines. The most commonly reported reasons for not intending to receive H1N1 vaccine were belief in a low likelihood of infection (18%) and concern over vaccine side effects (14%); 85% of participants said they received their H1N1 information from television. To increase coverage with H1N1 and seasonal influenza vaccines, public health departments should use television to focus public health messages on the risks for infection and severe illness and the safety profile of the vaccine.

Alamance and Orange counties were selected for the assessment because they were convenient venues with population age distributions similar to those for all of North Carolina. However, the education and race/ethnicity profiles of the two counties differ substantially from those of the entire state (Table 1), and Orange County has a generally higher socioeconomic status. A two-stage sampling method consisting of 30 random census tracts with seven randomly distributed households within each tract was used to identify 210 target households in the two counties, using parcel maps and a geographic information system-based toolkit. This sampling and data collection method, developed by CDC and referred to as Community Assessment for Public Health Emergency Response (CASPER),† has been validated and used effectively in postdisaster settings (4).

At the time of the survey, in late August 2009, H1N1 vaccine was in production but had not yet been approved by the Food and Drug Administration and released. Based on information available at the time, the survey assumed that 2 doses might be needed for adults and children. After the survey was completed, a single dose of vaccine was determined to be sufficient for persons aged ≥10 years.

During August 28--29, 2009, the assessment team visited the 210 households initially targeted. If no one answered at a household or the residents declined to participate, team members visited immediate neighboring households until an interview was completed. Oral informed consent was obtained, and responses were recorded using handheld computers. Household respondents aged ≥18 years represented themselves in the interviews and also any children in the household for questions pertaining to children aged <18 years. The survey consisted of 26 questions and required about 15 minutes to administer. Most questions required a yes/no response, including: "Are you aware that a pandemic H1N1 (or swine flu) vaccine is in production?" "Do you intend to receive the pandemic H1N1 vaccine when it becomes available [if the interviewee had no current knowledge, the interviewer prefaced this question with the fact that pandemic vaccine was in production]?" and "Do you intend to vaccinate all children in your household with pandemic H1N1 vaccine when it becomes available?" Additional questions pertained to prior history of and intent to receive seasonal influenza vaccine, reasons for intending or not intending to receive both vaccines (by selecting one or more from a list of 12 reasons), and level of concern about acquiring H1N1 illness (not at all, somewhat, or very concerned).

Of 258 houses at which a resident answered the door, 207 (80%) interviews were completed; 51 interviews were not completed because the residents declined participation. The median age of respondents was 49 years (range: 18--92 years), and 116 (56%) were female; 140 (68%) were non-Hispanic white, 52 (25%) were non-Hispanic black, and seven (3%) were Hispanic. A total of 165 (80%) respondents were aware that an H1N1 vaccine was in production, but only 75 (36%) were aware that the vaccine might require 2 doses for some persons. Knowledge about H1N1 vaccine was obtained from multiple sources: 85% received information from television, 52% from newspapers, 46% from radio, 36% from the Internet, and 35% from family or friends.

A total of 133 (64%) respondents reported intent to receive the H1N1 vaccine, and 109 (53%) intended to receive both vaccines (Table 2). Young adults aged 18--24 years (64%) were as likely to report intent to receive H1N1 vaccine as persons aged ≥65 years (66%). However, a greater percentage of persons aged ≥65 years (66%) reported intent to receive both H1N1 and seasonal influenza vaccines than persons aged 18--24 years (45%). Among 74 households with children aged <18 years, 48 (65%) respondents reported intent to vaccinate all their children with H1N1 vaccine; 38 (51%) said they would have all their children vaccinated with both H1N1 and seasonal influenza vaccines.

Among 74 (36%) respondents reporting no intent to receive H1N1 vaccine, reasons included the belief that they were unlikely to be infected (18%), concern over vaccine side effects (14%), a perception that if infected the illness would be mild (12%), the belief they were not included in a vaccination priority group (11%), and the inconvenience of a vaccine that might require 2 doses (8%). Intent to receive H1N1 vaccine was associated with intent to receive the 2009--10 seasonal influenza vaccine (prevalence ratio [PR] = 2.6), a high level of concern over becoming ill with the H1N1 virus (PR = 1.9), and previous 2008--09 influenza vaccination (PR = 1.5) (Table 3). Age, sex, and race/ethnicity were not associated with reported intent to receive H1N1 vaccine.

Editorial Note:

This report describes a novel use of CASPER methodology to measure community knowledge of and intent to receive H1N1 and seasonal influenza vaccines. The results indicate that, in late August 2009, the majority of the North Carolina interviewees were aware that an H1N1 vaccine was in production. Among all respondents, 64% reported intent to receive the H1N1 vaccine, a finding consistent among age groups, among racial/ethnic populations, and by sex. By comparison, national assessments conducted during May 26--June 8 and September 14--20 estimated intent among adults to receive H1N1 vaccine at 50% (1) and 53% (2) and intent to have their children vaccinated at 70% (2). Although the assessment described in this report is not entirely comparable to the national studies (in part because of different methodologies), the findings in this report are similar to the second study (2) regarding the two leading reasons offered by respondents for not intending to receive H1N1 vaccine: belief of a low risk for infection and concern over possible vaccine side effects.

The relationship between intent to receive vaccine and actual vaccination has not been well studied. For the assessment described in this report, no vaccine coverage data were available for the two counties. However, intentions to receive H1N1 vaccine (64%) and both H1N1 and 2009--10 seasonal influenza vaccines (54%) were substantially higher than the 33% coverage rate reported for seasonal influenza vaccine among the U.S. population during the 2008--09 season, the most recent data available (5). Intent to receive H1N1 vaccine among adults aged ≥65 years (66%) was similar to the seasonal influenza vaccination coverage rate of 65% for that age group reported nationally for 2008--09 (5). Additional research on the relationship between intent to receive vaccine and subsequent vaccination is needed.

The finding that respondents received H1N1 vaccine information primarily from popular media, particularly television, affirms the need for public health agencies to work closely with those media outlets most commonly used by the public. Public health agencies might be able to increase vaccination coverage by providing more information regarding 1) who should receive the vaccine first, 2) safety characteristics of the vaccine, and 3) severe illness that can be prevented by vaccination.

The findings in this report are subject to at least three limitations. First, the survey sample size was small, which reduced the precision of the estimates, especially for smaller subgroups. Second, the results are representative only of the populations of the two counties and are not generalizable to the entire population of North Carolina. Finally, widespread media coverage and face-to-face interviews might have increased the possibility of social desirability bias, resulting in an overestimate of the percentage of participants with intent to be vaccinated.

Influenza vaccination is the most effective method for preventing influenza and influenza-related complications. Currently available seasonal vaccine is unlikely to be protective against H1N1 (6). CDC has issued recommendations for use of influenza A (H1N1) 2009 monovalent vaccine (7).

Jackson LA, Neuzil KM, Baggs J, et al. Compliance with the recommendations for 2 doses of trivalent inactivated vaccine in children <9 years of age receiving influenza vaccine for the first time: a Vaccine Safety Datalink study. Pediatrics 2006;118:2032--7.

Two previous studies of intent to receive influenza A (H1N1) 2009 monovalent vaccine estimated potential vaccination coverage at 50%--53% for adults and 70% for children, using nationally representative samples and online or telephone survey methods.

What is added by this report?

This survey, conducted in August 2009 before the release of H1N1 vaccine, estimated intent to receive the vaccine in two North Carolina counties at 64% for adults and 65% for children; those with no intent cited belief in a low likelihood of infection (18%) and concern over vaccine side effects (14%), and 85% of participants said they received their H1N1 information from television.

What are the implications for public health practice?

To increase coverage with H1N1 influenza vaccine, public health departments should use television to focus public health messages on the risk for infection and severe illness and the safety profile of the vaccine.

TABLE 1. Percentage of population by age group, race/ethnicity, and education level --- Alamance and Orange counties and North Carolina, 2008

TABLE 2. Number and percentage of persons reporting intent to receive influenza A (H1N1) 2009 monovalent vaccine and intent to receive both H1N1 and seasonal influenza vaccines, by knowledge of vaccine, age group, race/ethnicity, and sex --- Alamance and Orange counties, North Carolina, August 2009

Total respondents (N = 207)

Intent to receive H1N1 vaccine (n = 133)

Intent to receive both H1N1 and seasonal influenza vaccine (n = 109)

Characteristic

No.

No.

%

(95% CI)

No.

%

(95% CI)

Knowledge of vaccine*

165

103

62

(53--71)

86

52

(41--63)

Age group (yrs)

18--24

22

14

64

(36--89)

10

45

(14--76)

25--64

138

88

64

(54--74)

68

49

(37--61)

≥65

47

31

66

(49--83)

31

66

(49--83)

Children aged <18 yrs†

74

48

65

(51--79)

38

51

(35--67)

Race/Ethnicity§

White, non-Hispanic

140

87

62

(52--72)

75

54

(43--65)

Black, non-Hispanic

52

36

69

(54--84)

28

54

(36--72)

Sex

Male

91

61

67

(55--79)

49

54

(40--68)

Female

116

71

61

(51--73)

59

51

(38--64)

* A "yes" response to the question, "Are you aware that a pandemic H1N1 (or swine flu vaccine is in production?"

† Respondents reported intent to vaccinate all children in their household aged <18 years with H1N1 vaccine or with both H1N1 and seasonal influenza vaccines.

§ Sample sizes for other race/ethnicities were too small to provide reliable estimates.

* In response to the question, "Are you aware that a pandemic H1N1 (or swine flu) vaccine is in production?"

† In response to the question, "How concerned are you about becoming sick with the pandemic H1N1 virus?"

§ In response to the question, "Did you receive seasonal influenza vaccine last year?"

¶ In response to the question, "Do you intend to receive the seasonal influenza vaccine this year?"

** In response to the question, "Do you have children less than 18 years of age currently living in your home?"

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